Thanks to Bucardo team for responding my previous post. My cascaded slave replication works as expected.
Today I notice there is still something to do related with delta and track tables.
Single table replication scenario:
Db-A/Tbl-T1 (master) => Db-B/Tbl-T2 (slave) => Db-C/Tbl-T3 (cascaded slave)
Every change on Table T1 replicated to T2, then T2 to T3. After a while, VAC successfully cleans delta and track tables on Db-A. But not on Db-B.
I detect 2 issues:
1. If cascaded replication T2 to T3 successful, the delta table on Db-B is not be cleaned up by VAC.
2. If cascaded replication T2 to T3 failed before VAC schedule, the delta table on Db-B will be cleaned up by VAC. Then, cascaded replication from T2 to T3 losts.
I fix it by modifying SQL inside bucardo.bucardo_purge_delta(text, text) in Db-A and Db-B:
— 1) Have been used by all dbgroups listed in bucardo_delta_targets
— 2) Have a matching txntime from the track table
— 3) Are older than the first argument interval
myst = 'DELETE FROM bucardo.'
|| ' USING (SELECT track.txntime AS tt FROM bucardo.'
|| ' track INNER JOIN bucardo.bucardo_delta_targets bdt ON track.target=bdt.target'
|| ' WHERE bdt.tablename::regclass::text='
|| ' GROUP BY 1 HAVING COUNT(*) = '
|| ') AS foo'
|| ' WHERE txntime = tt'
|| ' AND txntime < now() – interval '
Need advice from Bucardo team.